1. Field of the Invention
The present invention relates to a keyboard including a plurality of keys, more specifically, to a structure for supporting the keys of the keyboard.
2. Description of the Related Art
Known keyboards for use with electrical devices such as personal computers and word processors include a key top having a sliding unit on its inner surface and a base having a cylindrical guide. The sliding unit is slidably connected to the guide so as to move vertically (See Japanese Unexamined Patent Application Publication No. 11-3158 (hereinafter Document 1), in particular, FIG. 13 and Japanese Unexamined Utility Model Registration Application Publication No. 4-76224 (hereinafter Document 2), in particular, FIG. 3). Upon depression of the key by an operator, the key top is pressed down and the sliding unit comes into contact with a contact to input data that the key represents and the sliding unit is then returned to its original position by an elastic member such as a spring or a rubber piece.
Unfortunately, keyboards of this type have a drawback in that a short sliding unit and guide in a low-profile construction render the key top loose and unstable since the position of the key top is fixed by connecting the sliding unit to the guide (See page 2 in Document 2 and Japanese Unexamined Patent Application Publication No. 6-36647 (hereinafter Document 3), in particular, paragraph 0003). In this regard, this type of keyboard is unsuitable for low-profile or miniaturized constructions.
To this end, keyboards free from the aforementioned sliding unit and guide are being developed. A keyboard of an improved type includes key tops, each having a support composed of two hinges and a switch. In this keyboard, two hinges are fixed to an inner surface of a key top and a base such that the hinges are intersected when viewed from the side. The hinges are movably engaged with one another at the pivotal axis of the intersection. The top end of the hinge is slidably connected to a holding portion provided on the inner surface of the key top and the bottom end of the hinge is slidably connected to a holding portion provided on the base (See claim of Document 2 and claim 1 of Document 3).
Another improved keyboard has a supporting structure such that at least two hinges incline outward from the base. These hinges are disposed orthogonal to each other but not intersected when viewed from the top. These hinges are provided for each key such that top ends of the hinges are pivotally connected to the inner surface of the key top, and the bottom ends of the hinges are slidably connected to a base (See Japanese Unexamined Patent Application Publication No. 11-16440 (hereinafter Document 4), in particular, claim 1 and FIGS. 1–6).
These known keyboards described in Documents 2 to 4 require separate hinges for each key and assembly of the separate hinges.